Webster's English Dictionary

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luminescence

lu.mi.nes.cence \.lu:-m*-'nes-*n(t)s\ n 1: an emission of light that is not 
   ascribable directly to incandescence an d therefore occurs at low 
   temperatures and that is produced by physiological processes (as in the 
   firefly), by chemical action, by friction, or by electrical action 2: the 
   light produced by luminescence